System and method to provide fast wide-area mobile IP handoffs

ABSTRACT

A system, device, and method for real-time handoff in a mobile IP network is provided. In an embodiment, an indication that a mobile device is in a new network is sent out more often in a beacon than in an IRDP message in order to provide an effective seamless connectivity between service areas for wireless communications.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of and claims priority to U.S.Non Provisional patent application Ser. No. 12/250,372, filed on Oct.13, 2008, entitled “System and Method to Provide Fast Wide-Area MobileIP Handoffs.” This application, including all disclosures andspecifications of which, is hereby expressly incorporated herein byreference in its entirety.

FIELD OF INVENTION

The present invention relates generally to wireless communication, andmore particularly to methods, devices and systems for faster layer 3handoff across different layer 3 networks to minimize communicationdisruption period when moving between access points and/or to enableseamless handoff over wide geographical networks.

BACKGROUND

The Internet essentially consists of several protocols, of whichTransmission Control Protocol (TCP) and Internet Protocol (IP) arecommonly used protocols. IP, for example, requires the location of anynode connected to the network to be assigned a unique IP address. IP wascreated on the assumption that a single assigned IP address wassufficient to enable a node to access the Internet. The introduction ofmobile nodes, which today include portable computers, cellulartelephones, media players, and other mobile devices, introduced achallenge that IP did not address, namely, the situation when a nodemoves to a new physical location, it must, pursuant to IP, change its IPaddress. Mobile Internet Protocol (Mobile IP or MIP), among others, wascreated to address this challenge. Mobile IP is a standardcommunications protocol designed by the Internet Engineering Task Force(IETF) and enables mobile nodes to remain connected to a networkregardless of their locations and without changing their respective IPaddresses.

Mobile IP enables node mobility by binding the mobile node's homeaddress to a care-of address. The home IP address and the care-ofaddress are maintained in specialized routers called mobility agents.There are two types of mobility agents: home agents and foreign agents.The home agent is a router in a home network associated with the mobilenode which maintains the mobility binding in a mobility binding table.Foreign agents are specialized routers on the foreign network visited bythe mobile node. The foreign agent maintains a visitor list whichcontains information about the mobile nodes currently visiting thatnetwork. Typically, the care-of address is the foreign agent's IPaddress. Mobility agents advertise their presence and availability tomobile nodes by periodically (for instance, once every three seconds)broadcasting an IRDP (Internet Control Message Protocol (ICMP) RouterDiscovery Protocol) message listing one or more care-of addresses which,when received by a mobile node, may result in the mobile node requestingregistration with the home agent. The mobile node receives an IRDPmessage from the new foreign agent in order to determine that it hasroamed on a new network and before it can register with the home agentvia the foreign agent. Since IRDP messages are sent periodically (e.g.,every three seconds), mobile node users experience service interruptionscaused by the inherent registration delays. Once an IRDP messagecontaining the new foreign agent information is received by the mobilenode, the mobile node triggers the registration with the home agent viathe foreign agent. A successful Mobile IP registration sets up therouting mechanism between the home agent and the mobile node, as themobile node roams across different networks.

Accordingly, there are problems in the registration of mobile nodes withforeign agents, for example, those that result in slow or latent IPhandoffs causing a nonoptimal user experience. Many mobile nodes, suchas cellular telephones, in practical use, move rapidly across thephysical boundaries of foreign networks. Such mobile nodes are typicallyengaged in data sessions supporting a variety of user experiences,including, for instance, IP-based voice communications, or VoIP. VoIPgenerally requires its end-to-end delay to be lower than 250 ms, delayvariance or jitter lower than 50 ms, and packet loss rate less than 1%.The currently available handoff process utilizing IRDP cannot satisfythe requirements of real-time interactive application because thecommunication disruption period is too long and the long communicationdisruption causes packet loss. Thus, a mobile node user engaged in adata session can experience service interruption or even loss of serviceif the mobile node moves into a new network or region area.

Further, building out an entire network using layer 2 has scalabilityissues such as broadcasts, multicasts and slow spanning treeconvergence. Some very large layer 2 networks have been built, buteventually there is an upper limit to the number of nodes that can bedeployed in the same layer 2 network. Similarly, building out the entirenetwork using layer 3 involves latency issues due to the fact thatrouters do their work in software and not in hardware. An availablemethod mixes layers 2 and 3. In practical application, approximatelysixty to ninety nodes are bundled into a regional layer 2 network, orregion. An intra-region handoff is via layer 2 and inter-region handoffsrequire both a layer 2 and a layer 3 handoff.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide effectively seamlesswireless communication between different regions. Further embodiments ofthe present invention provide methods, devices and systems for fastlayer 3 handoff to minimize communication disruption period which occurswhen a mobile node moves away from its current access point associatedwith a first mobility agent and to a new access point associated with asecond mobility agent.

Embodiments of the present invention include methods, devices, andsystems for completing rapid foreign IP registration, thus permitting arapid, seamless handoff of mobile node registration between foreignnetworks. To accomplish effectively seamless real-time handoff or rapidhandoff in a Mobile IP network, an embodiment of the present inventionprovides a system and method for expediting the handover process acrosslayer 3 boundaries. In an embodiment, the handover process speeds up themobile IP registration process across layer 3 boundaries for networkdeployments such as linear meshes for trains and subways, andtwo-dimensional meshes like metro Wi-Fi and access point or meshdeployments in airports, hotel complexes, malls, large buildings andstadiums. In an embodiment, the handover process speeds up the mobile IPregistration process from one conventional access point on one networkto another conventional access point on another network.

Rapid registration with a home agent is an essential requirement forVoIP and other real time data services like video and audio streaming,and video conferencing. Because the IRDP messages rarely change, in anembodiment, the care-of-address and/or some other parameters from themost recent IRDP message are stored. Further, those parameters are sentin management packets of any wireless or wired networks that are sentmore often than the IRDP messages such as beacons and probe responses in802.11. Since the mobile node must read the beacon or probe response aspart of a layer 2 handoff, that information is then used to expedite theagent discovery process which triggers the mobile IP registration whichis part of the layer 3 handoff. Such embodiments provide for fasterhandovers for real-time applications such as UMA calls, voice over IPcalls, video applications, etc. in milliseconds rather than seconds, andfewer dropped sessions. Also, data applications such as web browsing,FTP, audio streaming also have enhanced performance during handoffs.

An embodiment of the present invention provides a method and a systemperformed via an access point for facilitating rapid handoffs in amobile network, including: receiving at least one service availabilityadvertisement; extracting service availability content from the at leastone service availability advertisement; appending the serviceavailability content into at least one rapidly repeated managementpacket transmission; and transmitting the appended rapidly repeatedmanagement packet transmission. In an embodiment, the appended rapidlyrepeated management packet is transmitted more frequently than the atleast one service availability advertisement is received. In anembodiment, the service availability content includes at least one of:an address of a foreign agent, a Registration Lifetime, a number of Careof Addresses, at least one Care of Address, a home agent flag, and aforeign agent flag. In an embodiment, the at least one serviceavailability advertisement includes an Internet Control Message ProtocolRouter Discovery Protocol (IRDP) message. In an embodiment, the mobilenetwork is a Mobile Internet Protocol (IP) network and the rapidhandoffs occur via Layer 3. In an embodiment, the at least one rapidlyrepeated management packet is one of a beacon message and a proberesponse. In an embodiment, the at least one service availabilityadvertisement is received from a layer 2 region. In an embodiment, theat least one service availability advertisement indicates soon-entryfrom a first layer 2 region to a second layer 2 region, the first andsecond layer 2 regions being different.

An embodiment of the present invention provides a method and systemperformed via a mobile node for facilitating rapid handoffs in a mobilenetwork, including: receiving a management packet having serviceavailability content; extracting the service availability content fromthe management packet; composing a network registration message basedupon the extracted service availability content; and transmitting thenetwork registration message. In an embodiment, the management packet isone of a beacon message and a probe response. In an embodiment, thefacilitating of rapid handoffs occurs via Layer 3 of a Mobile IPnetwork. In an embodiment, the service availability content includes atleast one of: an address of a foreign agent, a Registration Lifetime, anumber of Care of Addresses, a Care of Address, a home agent flag, and aforeign agent flag. In an embodiment, the service availability contentincludes an IRDP message.

An embodiment of the present invention provides a method and system forfacilitating rapid Layer 3 handoffs in a mobile Internet Protocol (IP)network, including: providing an access point; and providing a mobilenode, the mobile node being initially connected to a different accesspoint. The access point receives at least one service availabilityadvertisement; extracts service availability content from the at leastone service availability advertisement; appends the service availabilitycontent into at least one rapidly repeated management packettransmission; and transmits the appended rapidly repeated managementpacket transmission. The appended rapidly repeated management packet istransmitted more frequently than the at least one service availabilityadvertisement is received. The mobile node receives the appendedmanagement packet transmission, extracts the service availabilitycontent from the appended management packet transmission; composes anetwork registration message based upon the extracted serviceavailability content; and transmits the network registration message. Inan embodiment, the at least one service availability advertisementindicates soon-entry from a first layer 2 region to a second layer 2region, the second layer 2 being associated with the access point, thefirst and second layer 2 regions being different. In an embodiment,after the mobile node receives the appended management packettransmission, the at least one rapidly repeated management packet isvalidated by the mobile node. In an embodiment, the service availabilitycontent includes at least one of: an address of a foreign agent, aRegistration Lifetime, a number of Care of Addresses, at least one Careof Address, a region indicator integer, a home agent flag, and a foreignagent flag. In an embodiment, the region indicator integer is stored inan object identifier preprogrammed in the associated access point viathe at least one service availability advertisement. The regionindicator integer may represent a specific region of coverage by theassociated access point. In an embodiment, the appending of the serviceavailability content into at least one rapidly repeated managementpacket transmission includes generating a new field in a managementframe of the management packet, the new field being populated with theIRDP message. In an embodiment, the at least one service availabilityadvertisement includes an Internet Control Message Protocol RouterDiscovery Protocol (IRDP) message. In an embodiment, the at least onerapidly repeated management packet is one of a beacon message and aprobe response. In an embodiment, the access point transmits IRDPmessages at a further reduced rate. In an embodiment, after the mobilenode receives the appended management packet transmission, validatingthe at least one rapidly repeated management packet by the mobile nodeincluding: identifying an SSID and a Care of Address in a managementframe of the management packet, confirming that the SSID is valid,confirming that the Care of Address is an available Care of Address,wherein if both the SSID and Care of Address are successfully confirmed,then the composing of the network registration message includesgenerating the SSID and the Care of Address into a new serviceavailability advertisement which is transmitted as the networkregistration message. In an embodiment, if at least one of the SSID isconfirmed as invalid and the Care of Address is confirmed asunavailable, then the mobile node discards the management packet. In anembodiment, the transmission of the network registration messageinvolves a registration of location by the mobile node with a home agentof the mobile node via the access point. In an embodiment, after theaccess point extracts service availability content from the at least oneservice availability advertisement, then the service availabilitycontent is stored in a table. In an embodiment, the table is at leastone of local to the access point, remote to the access point, and may becomposed of a plurality of tables. In an embodiment, after the mobilenode receives the appended management packet transmission, the at leastone rapidly repeated management packet is validated by the mobile nodeincluding: identifying an SSID and a region indicator integer in amanagement frame of the management packet, confirming that the SSID isvalid, and confirming that the region indicator integer identifies a newregion, wherein the new region associated with the new region indicatorinteger is different than a current region of the mobile node. In anembodiment, if both the SSID and the region indicator integer aresuccessfully confirmed, then the mobile node uses the region indicatorinteger to retrieve service availability content associated with theregion indicator integer from the table. In an embodiment, the retrievedservice availability content is used to generate a new serviceavailability advertisement to be sent to the mobile node. In anembodiment, handoff to a new access point in a same region as the mobilenode, using the region indicator integer, is effected before handoff toa new access point in a different region than the mobile node.

An embodiment of the present invention provides a method and systemperformed via an access point for facilitating real-time layer 3 handoffin a mobile IP network, including: receiving a management frame;identifying a Service Set Identifier (SSID) and a Care of Address withinthe management frame; confirming that the SSID is valid; confirming thatthe Care of Address is available; appending the valid SSID and theavailable Care of Address into a beacon message; and transmitting theappended beacon message. In an embodiment, the appended beacon messageis transmitted more frequently than the receipt of the management frame.In an embodiment, the appended beacon message is received by a mobilenode.

An embodiment of the present invention provides a system and method forfacilitating rapid layer 3 handoff in a mobile IP network, including; amobile node; a first access point in a first region, the mobile nodebeing connected to the first access point and having an associated firststrength of connection; a second access point in a second region,wherein upon approaching the second region, the mobile node: scans forthe second access point, the second access point broadcasting one of abeacon and a probe response so that the scanning mobile node identifiesthe second access point, the one of the beacon and the probe responsebeing broadcasted at shorter time intervals than an IRDP advertisement,determines a potential second strength of connection with the secondaccess point, compares the first strength of connection with thepotential second strength of connection, and if the first strength ofconnection is less than the potential second strength of connection,then the mobile node changes connection from the first access point tothe second access point. In an embodiment, the mobile node scans for thesecond access point when the first strength of connection reaches apredetermined level. In an embodiment, one of the beacon and proberesponse has a frame header and a frame body. In an embodiment, theframe header includes a source and destination Medium Access Control(MAC) addresses. In an embodiment, the frame body includes at least oneof a Service Set Identifier (SSID), a timestamp, a transmissioninterval, a parameter set, the parameter set including IRDP messageinformation which had been extrapolated from the IRDP advertisement, aRegistration Lifetime, a home agent flag, and a foreign agent flag. Inan embodiment, the mobile node changes connection from the first accesspoint to the second access point only upon successful authentication ofthe SSID.

An embodiment of the present invention provides a system and method forreal-time handoff in a mobile IP network, including: an access point;and a mobile node. The access point receives at least one serviceavailability communication, extracts service availability content fromthe at least one service availability communication, appends the serviceavailability content into a management packet, the management packetbeing one of a beacon message and a probe request, and transmits theappended management packet. The mobile node receives the appendedmanagement packet, extracts service availability content from theappended management packet, composes a network registration messagebased upon the extracted service availability content, and transmits thenetwork registration message to the network. In an embodiment, the atleast one service availability communication includes an IRDP message.In an embodiment, after the mobile node receives the appended managementpacket, the mobile node validates the management packet. In anembodiment, the service availability content includes at least one of:an address of a foreign agent, a Registration Lifetime, a number of Careof Addresses, a Care of Address, a region indicator integer, a homeagent flag, and a foreign agent flag. In an embodiment, the regionindicator integer is stored in an object identifier preprogrammed in theassociated access point via the at least one service availabilityadvertisement. The region indicator integer represents a specific regionof coverage by the associated access point. In an embodiment, theappending of the service availability content into a management packetincludes generating a new field in a management frame of the managementpacket, the new field being populated with the IRDP message. In anembodiment, the access point transmits IRDP messages at a furtherreduced rate to prevent congestion, and a plurality of access points aredeployed at and near region boundaries. In an embodiment, after themobile node receives the appended management packet transmission, the atleast one rapidly repeated management packet is validated by the mobilenode including: identifying an SSID and a Care of Address in amanagement frame of the management packet, confirming that the SSID isvalid, and confirming that the Care of Address is an available Care ofAddress. In an embodiment, if both the SSID and Care of Address aresuccessfully confirmed, then the composing of the network registrationmessage includes generating the SSID and the Care of Address into a newservice availability advertisement which is transmitted as the networkregistration message. In an embodiment, if at least one of the SSID isconfirmed as invalid and the Care of Address is confirmed asunavailable, then the mobile node discards the management packet. In anembodiment, the transmission of the network registration messageinvolves a registration of location by the mobile node with a home agentof the mobile node via the access point. In an embodiment, after theaccess point extracts service availability content from the at least oneservice availability advertisement, then the service availabilitycontent is stored in a table, the table being at least one of local tothe access point, remote to the access point, and composed of aplurality of tables. In an embodiment, after the mobile node receivesthe appended management packet transmission, the at least one rapidlyrepeated management packet is validated by the mobile node including:identifying an SSID and a region indicator integer in a management frameof the management packet, confirming that the SSID is valid, confirmingthat the region indicator integer identifies a new region, wherein thenew region associated with the new region indicator integer is differentthan a current region of the mobile node, wherein if both the SSID andthe region indicator integer are successfully confirmed, then the mobilenode uses the region indicator integer to retrieve service availabilitycontent associated with the region indicator integer from the table. Inan embodiment, the retrieved service availability content is used togenerate a new service availability advertisement to be sent to themobile node. In an embodiment, handoff to a new access point in a sameregion as the mobile node, using the region indicator integer, iseffected before handoff to a new access point in a different region thanthe mobile node.

An embodiment of the present invention provides for a system and methodfor real-time handoff in a mobile IP network when a management frame isreceived by a mobile node, including: a mobile node; a management frameassociated with a management packet received by the mobile node,wherein: the mobile node determines whether the management frameincludes a valid Service Set Identifier (SSID) and an available new Careof Address (CoA); the mobile node generates a new IRDP message upondetermining that the management frame includes the valid SSID and theavailable new CoA; and the mobile node transmits the new IRDP message toat least one mobile router, wherein the mobile router initiates aregistration process after receiving the new IRDP message.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a mobile IP group for handover in a mobile communicationsystem.

FIG. 2A shows a process flow of a handover message flow in a mobilecommunication system.

FIG. 2B shows a flowchart of a handover process flow in a mobilecommunication system.

FIG. 3 is a diagram showing a standard access point beacon frame.

FIG. 4A is a diagram illustrating an example of the updated access pointbeacon frame according to an embodiment of the invention.

FIG. 4B is a diagram illustrating an example of the updated access pointbeacon frame according to an embodiment of the present invention.

FIG. 5A shows a message flow according to an embodiment of the presentinvention.

FIG. 5B shows a flow chart of a handover process flow in a mobilecommunication system according to an embodiment of the presentinvention.

FIG. 6A is a message flow showing a handover process according to anembodiment of the present invention.

FIG. 6B is a flow chart showing a handover process according to anembodiment of the present invention.

DETAILED DESCRIPTION

The following description provides specific details for a thoroughunderstanding of, and enabling description for, various embodiments ofthe technology. One skilled in the art will understand that thetechnology may be practiced without many of these details. In someinstances, well-known structures and functions have not been shown ordescribed in detail to avoid unnecessarily obscuring the description ofthe embodiments of the technology. It is intended that the terminologyused in the description presented below be interpreted in its broadestreasonable manner, even though it is being used in conjunction with adetailed description of certain embodiments of the technology. Althoughcertain terms may be emphasized below, any terminology intended to beinterpreted in any restricted manner will be overtly and specificallydefined as such in this Detailed Description section.

Embodiments of the present invention provides methods, devices andsystems for performing fast layer 3 handovers of wireless servicebetween access points of IP-based wireless networks.

Embodiments of the present invention relates to wireless communicationsdevices and wireless communication systems. The former are referred tohere as mobile nodes, such as laptop computers, cellular telephones,smart phones, media players and other mobile devices. The latter isreferred to here as access points and the network(s) behind them, suchas interconnected routers and servers, which provide services such asdata communications to mobile nodes. Various inventive concepts of theinvention are embodied in mobile nodes and access points, as well asmethods used therein for providing a handoff of data communicationsservices between nodes of a wireless network through a system of IRDPmessages advertised by foreign agents as the user roams across variousgeographic domains.

As discussed above, Mobile IP provides an IP-based mobility solutionthat allows mobile nodes to maintain network connectivity whileretaining their home network IP addresses. For example, it enables thenode mobility to be transparent to all executing applications byproviding the node with a care-of-address that can be registered with ahome agent, thereby ensuring that packets are quickly forwarded to themobile's current location in the foreign network.

Mobility binding is maintained by specialized routers known as mobilityagents, either home agents and foreign agents. The home agent is adesignated router in the mobile node's home network, and maintains amobility binding table in which each entry is identified by the tuple<permanent home address, temporary care-of address, associationlifetime>. Foreign agents are specialized routers on the foreign networkthat the mobile node is visiting. The foreign agent maintains a visitorlist containing information about the mobile nodes visiting the foreignnetwork. Each entry in the visitor list is identified by the tuple:<permanent home address, home agent address, media address of the mobilenode, association lifetime>. The care-of address is usually the foreignagent's IP address.

Mobile IP includes three sub processes. First, a mobile node mustdiscover its foreign and home agents during agent discovery. Mobilityagents advertise their availability to mobile nodes by periodicallybroadcasting IRDP messages. An IRDP message includes one or more care-ofaddresses and a flag indicating whether it is a home agent or a foreignagent. When a mobile node enters the mobile agent's network area, itreceives the IRDP message broadcasted via one or more access points.Second, the mobile node must register its current location with theforeign agent and home agent during registration. The mobile nodedetermines whether the message is from its own home agent or a foreignagent. If the message is from the mobile node's home network, itoperates without any mobility services. If the message is from a foreignagent, however, then the mobile node must register with the foreignagent. This is accomplished by sending a registration request messagewhich includes, among other things, the permanent IP address of themobile host and the IP address of its home agent. The foreign agent thensends a registration request containing the mobile node's permanent IPaddress and the foreign agent's IP address to the home agent. When thehome agent receives the registration request, it updates the mobilitybinding by associating the care-of address of the mobile node with itshome address. The home agent then sends a registration acknowledgementto the foreign agent. The foreign agent in turn updates its visitor listby inserting the entry for the mobile node and relays the reply to themobile node. Finally, a reciprocal tunnel is set up by the home agent tothe care-of address (current location of the mobile node on the foreignnetwork) to route packets to the mobile node as it roams. The mobilenode may engage in data sessions with a correspondent node (e.g., aWebsite, another mobile node). For instance, a correspondent node maysend an IP packet addressed to the permanent IP address of the mobilenode. The home agent intercepts the packet and checks its mobilitybinding table to learn whether the mobile node is visiting a foreignnetwork. The home agent can then route the IP packets to the care-ofaddress by constructing a new IP header that contains the mobile node'scare-of address as the destination IP address. The original IP packet isincluding in the IP packet's payload. The home agent then transmits thepacket. When the encapsulated packet reaches the foreign network servingthe mobile node, the foreign agent decapsulates the IP packet and learnsthe mobile node's home address. It then consults its visitor list tolearn whether there is an entry for the mobile node. The foreign agentthen retrieves the corresponding media or MAC address and relays it tothe mobile node. The foreign agent continues serving the mobile nodeuntil the granted lifetime expires. If the mobile node wants to continuethe service, it has to reissue the Registration Request.

FIG. 1 shows an example of the system architecture utilizing Mobile IPaccording to a conventional mobile communication system. FIG. 1 shows anInternet 100, a core network 102, home agent (HA) 104, foreign agents(FA) 106, 108, layer 3 (L3) transport network 110, one layer 2 (L2)regional IP network 112 and its access points 114 a, 114 b, 114 c, asecond layer 2 (L2) regional IP network 113 and its access points 120 a,120 b, 120 c, and a mobile node 116. The home agent 104 and the foreignagents 106, 108 run Mobile IP. The home agent 104 rather than routingtraffic by subnet or IP address, encapsulates traffic and routes itthrough the correct foreign agent and layer 2 regional IP networkaccording to the care-of address. Mobile node 116 can be connected toany of access points 114 a, 114 b, 114 c in the same regional networkand perform a layer 2 handoff to connect to another access point 114 a,114 b, 114 c. No layer 3 handoff is required because the relevant accesspoints 114, 114 b, 114 c are in the same layer 2 network. Mobile node116 can be associated with, for example, an access point 114 a, 114 b,114 c in a first regional network 112 and may also perform a layer 2handoff to connect with, for example, an access points 120 a, 120 b, 120c in a different regional network 113. In this case, however, a layer 3handoff must also be completed because a move between one or more accesspoints 114 a, 114 b, 114 c in a first network or region to one or moreaccess points 120 a, 120 b, 120 c in a second network or region are notin the same layer 2 network or region. Embodiments of the presentinvention provide for an efficient handoff between networks or regions,effecting a layer 3 handoff.

FIGS. 2A and 2B illustrate flow charts showing a handover process flowin a conventional Mobile IP communication system viewed in conjunctionwith FIG. 1 for example purposes. During the agent discovery phase, thehome agent 104 and foreign agents 106, 108 advertise their services ontheir respective networks 110, 112, 113 by sending out the ICMP RouterDiscovery Protocol (IRDP) messages 118 at regular intervals 250 towardsthe mobile node 116, this interval may be every 3 seconds (Step 200).For example, access point 120 a intercepts the IRDP message, stores itand updates the parameters sent out in the beacons that it regularlybroadcasts to mobile nodes (Step 202). The mobile node 116 listens tothe IRDP message advertisements 118 to determine if it is connected toits home network or foreign network (Step 204). If a mobile node 116determines that it is connected to a foreign network, it acquires acare-of address (Step 204).

There are two types of care-of addresses: a care-of address acquiredfrom a foreign agent and a colocated care-of address. A foreign agentcare-of address is typically an IP address of a foreign agent 106, 108that has an interface on the foreign network being visited by a mobilenode 116. A mobile node 116 that acquires this type of care-of addresscan share the address with other mobile nodes. A colocated care-ofaddress is an IP address temporarily assigned to the interface of themobile node 116 itself. A colocated care-of address represents thecurrent position of the mobile node 116 on the foreign network and canbe used by only one mobile node 116 at a time. When the mobile node 116hears a new foreign agent 120 a IRDP advertisement and detects that ithas moved outside of its home network, it begins registration 252. In anembodiment, once an IRDP message 118 that includes information about anew foreign agent 108 is received by mobile node 116, the mobile node116 triggers the registration 252 with the home agent 104 via the newforeign agent 108 (Step 208).

The mobile node 116 is configured with the IP address and mobilitysecurity association (which includes the shared key) of its home agent104 (Step 210). Alternatively, the mobile node 116 can be configuredwith either its home IP address, or another user identifier, such as anetwork access identifier. The mobile node 116 uses this informationalong with the information that it learns from the foreign agent 108IRDP advertisements to form a Mobile IP registration request 252. Itadds the registration request to its pending list and sends theregistration request to its home agent 104 either through the foreignagent 108 or directly if it is using a colocated care-of address and isnot required to register through the foreign agent 108. If theregistration request is sent through the foreign agent 108, the foreignagent 108 checks the validity of the registration request (Step 212),which includes checking that the requested lifetime does not exceed itslimitations, the requested tunnel encapsulation is available, and thatreverse tunnel is supported. If the registration request is valid, theforeign agent 108 adds the visiting mobile node 116 to its pending listbefore relaying the request 254 to the home agent 104. If theregistration request is not valid, the foreign agent 108 sends aregistration reply with appropriate error code to the mobile node 116.

The home agent 104 checks the validity of the registration request (Step214), which includes authentication of the mobile node 116. If theregistration request is valid, the home agent 104 creates a mobilitybinding (Step 216) (an association of the mobile node with its care-ofaddress), a tunnel to the care-of address, and a routing entry forforwarding packets to the home address through the tunnel. The homeagent 104 then sends a registration reply 256 to the mobile node 116through the foreign agent 108 (if the registration request was receivedvia the foreign agent 108) or directly to the mobile node 116. If theregistration request is not valid, the home agent 104 rejects therequest by sending a registration reply with an appropriate error code.

The foreign agent 108 checks the validity of the registration reply(Step 218), including ensuring that an associated registration requestexists in its pending list. If the registration reply 256 is valid, theforeign agent 108 adds the mobile node 116 to its visitor list,establishes a tunnel to the home agent 104, and creates a routing entryfor forwarding packets to the home address. It then relays theregistration reply 258 to the mobile node 116.

Finally, the mobile node 116 checks the validity of the registrationreply (Step 220), which includes ensuring an associated request is inits pending list as well as proper authentication of the home agent 104.If the registration reply is not valid, the mobile node 116 discards thereply. If a valid registration reply specifies that the registration isaccepted, the mobile node 116 is confirmed that the mobility agents areaware of its roaming. In the colocated care-of address case, it adds atunnel to the home agent 104. Subsequently, the mobile node 116 sendsall packets to the foreign agent 108.

The mobile node 116 reregisters before its registration lifetimeexpires. The home agent 104 and foreign agent 108 update their mobilitybinding and visitor entry, respectively, during re-registration. In thecase where the registration is denied, the mobile node 116 makes thenecessary adjustments and attempts to register again. For example, ifthe registration is denied because of time mismatch and the home agent104 sends back its time stamp for synchronization, the mobile node 116adjusts the time stamp in future registration requests.

Thus, a successful Mobile IP registration sets up the routing mechanismfor transporting packets to and from the mobile node as it roams (Step222).

During the tunneling process 260, the mobile node 116 sends packetsusing its home IP address, effectively maintaining the appearance thatit is always on its home network. Even while the mobile node is roamingon foreign networks, its movements are transparent to correspondentnodes.

Data packets addressed to the mobile node 116 are routed to its homenetwork, where the home agent 104 now intercepts and tunnels 262 them tothe care-of address toward the mobile node 116. Tunneling has twoprimary functions: encapsulation of the data packet to reach the tunnelendpoint, and de-capsulation when the packet is delivered at thatendpoint. The default tunnel mode is IP encapsulation within IPencapsulation. Optionally, GRE and minimal encapsulation within IP maybe used. Typically, the mobile node 116 sends packets to the foreignagent 108, which routes them to their final destination.

The first and the slowest part of this three step process is the agentdiscovery phase. Currently, there is no mechanism described in RFC 1256by which the mobile node 116 can quickly discover that it is in a new orforeign network. The mobile node 116 has to wait for an IRDP message 118after it has completed a layer 2 handoff into the new region, before itcan complete the layer 3 handoff with Mobile IP. While one could sendIRDP messages 118 more often than once every three seconds, this maybreak RFC 1256's upper limit for how often an IRDP message can be sentand would flood the network with IRDP messages.

In an embodiment of the present invention, a mobile node does not waituntil it loses connectivity and/or experiences poor performance to seekalternative access points. In other words, in an embodiment of thepresent invention, a system is provided such that a mobile node may beproactive to ensure continued optimal performance rather than solely bereactive to perceived poor performance. For example, the scanning forthe best candidate access point 120 a may be accomplished beforebreaking the current connection. Therefore, if mobile node 116 isconnected to access point 114 c and a neighbor access point 120 a isavailable and can provide better link quality than the serving accesspoint 114 c, the mobile node may discover and connect with it before thecurrent link quality drops into a very poor status. Thus, when themobile node 116 finds a preferable access point 120 a, the handoff canbe completed by detaching from the serving access point 114 c and makingauthentication and new association with the new access point 120 a.

In accordance with an embodiment of the present invention, access pointmanagement frames carry the contents of the IRDP message correspondingto the foreign agent for the new location. In an embodiment, as soon asaccess point-mobile node authentication and association are complete,the Mobile IP registration process can begin earlier.

In a standard network using Mobile IP, an access point is responsiblefor transmitting beacon frames. The area in which beacon frames aretransmitted defines the access point's basic service area. Allcommunication in standard network is done through access points, somobile nodes on the network must be within the access point's servicearea to receive the access point's beacons. Access points broadcastbeacons many times a second in order to allow mobile nodes to quicklyfind and identify the basic service area.

FIG. 3 is a diagram showing a standard access point beacon frame. Anaccess point has only a wireless interface, via which all data, controland management frames (including beacon frames) are sent or received, sothe BSSID in the beacon frame is the MAC address used by this wirelessinterface access point, and the current channel, included in the DSparameter field, is just the working channel of this wireless interface.

An example beacon frame is approximately fifty bytes long, roughly halfof which is comprised by a common frame header and cyclic redundancychecking (CRC) field. As with other frames, the header includes sourceand destination MAC addresses as well as other information regarding thecommunications process. The destination address consists entirely ofones, which is the broadcast Medium Access Control (MAC) address. Thisforces all other stations on the applicable channel to receive andprocess each beacon frame. The CRC field provides error detectioncapability. The remainder of the beacon frame resides between the headerand the CRC field. Each beacon frame carries the following informationin the frame body:

-   -   Timestamp    -   Beacon interval    -   Capability information    -   Service Set Identifier (SSID)    -   DS parameters

FIG. 4A is a diagram illustrating an example of the updated access pointbeacon frame according to an embodiment of the present invention. Forthe DS parameter field, a new sub-field IRDP beacon is generated andinserted as part of an access point beacon or probe response managementframe. This parameter field in the management frame is populated withthe IRDP message information extrapolated from an incoming IRDP message.In particular, the parameter field includes the address of the foreignagent, the Registration Lifetime, the number of Care of Address(es),Care of Address(es), and flags R/B/H/F/M/G/V.

FIG. 4B is a diagram illustrating an example of the updated access pointbeacon frame or probe response according to an embodiment of the presentinvention. For the DS parameter field, a new sub-field IRDP beacon isgenerated and inserted as part of an access point beacon or proberesponse management frame. This parameter field in the management frameis populated with an unsigned integer region number. Simultaneously, theregion number is stored in a new OID (object identifier) which isprogrammed into the access point.

In accordance with an embodiment of the present invention, the speed ofdiscovery of new region and the corresponding registration phase may beincreased. Towards this end, an access point wireless component can beutilized. An access point management frame can carry the contents of anIRDP message or the representations thereof to the foreign agent for thenew location. As soon as the access point authentication and associationare complete, the Mobile IP registration process could get startedearlier.

FIGS. 5A and 5B illustrate process flows in accordance with anembodiment of the present invention. As described in FIGS. 2A and 2Babove, IRDP messages 118 are periodically sent between foreign agent 106and mobile node 116 (Step 502). When an IRDP message 118 is received ata access point 120 a, its contents are stored within access point 120 afor further processing (Step 504). The information of the IRDP message118 being stored includes but is not limited to the address of theforeign agent 108, the Registration Lifetime, the Number of Care ofAddress(es), Care of Address(es) (CoA), and flags R/B/H/F/M/G/V. Theaccess point 120 a beacons 550 and probe response 552 traverses thenetwork at a higher frequency compared to IRDP messages, when an accesspoint beacon or probe response needs to be transmitted, a special newfield in the management frame is generated and populated with the IRDPmessage information (Step 506). The message information may include,among other things, the address of the foreign agent 108, theRegistration Lifetime, the Number of Care of Address(es), Care ofAddress(es) (CoA), and flags R/B/H/F/M/G/V.

When an access point management frame is received at an mobile node 116,the mobile node determines the validity of the beacon or probe response(Step 508), which includes ensuring an associated beacon 550 or proberesponse 552 is in its pending list as well as proper authentication ofSSID (Step 510). If the SSID is not valid and/or the management framedoes not contain a new CoA, the mobile node 116 discards the beacon orprobe response and continues to receive other beacons or proberesponses. If a valid SSID is received and the management frame containsa new CoA, the management frame content is generated into a new IRDPmessage 554 that will be sent to the mobile router as soon as the mobilenode 116 is fully associated (Step 512). Alternatively, the newlyconstructed IRDP message can be transmitted to a mobile node 116 client.Once authentication and association is complete, the new IRDP message554 can be transmitted to the mobile node 116. Thereafter, the mobilenode 116 can register its current location with the home agent 104 viathe foreign agent 108 (Step 514).

FIGS. 6A and 6B illustrate process flows in accordance with anembodiment of the present invention. In an embodiment, IRDP messages 118are periodically sent between foreign agent 108 and mobile node 116(Step 602). When an IRDP message 118 is received at a access point 120a, its contents are stored within a table of regions for furtherprocessing (Step 604). In an embodiment, the table may be local orremote from the access point 120 a. Specifically, the information of theIRDP message 118 being stored on the table of regions includes but isnot limited to the address of the foreign agent 108, the RegistrationLifetime, the Number of Care of Address(es), Care of Address(es) (CoA),and flags R/B/H/F/M/G/V. In an embodiment, the use of a table of regionsassists in providing a more robust, automated system in providingincreased ease of identification of a new region or network.

The access point beacons 650 and probe response 652 traverses thenetwork at a higher frequency compared to IRDP messages, when an accesspoint beacon or probe response needs to be transmitted, a special newfield in the management frame is generated and populated with oneunsigned integer, wherein the unsigned integer represent a particularregion of coverage (Step 606). The region number is stored in a new OID(Object Identifier) which is programmed into the access point 120 a. Inan embodiment, the OID is preprogrammed into the access point 120 athrough an IRDP message 118 through foreign agent 108 or home agent 104.

When an access point management frame is received at a mobile node 116,the mobile node determines the validity of the beacon or probe response(Step 608), which includes ensuring an associated beacon 650 or proberesponse 652 is in its pending list as well as proper authentication ofSSID (Step 610). If the SSID is not valid and/or the management framedoes not contain a new region indication, the mobile node 116 discardsthe beacon or probe response and continues to receive other beacons orprobe responses. If a valid SSID is received and the management framecontains a new region indication, the region is used by the mobile node116 to retrieve corresponding data from the table or regions (Step 612).Next, the retrieved contents are used to generate a new IRDP message 654that will be sent to the mobile node 116 as soon as the mobile node 116is fully associated (Step 614). Once authentication and association iscomplete, the new IRDP message 654 can be transmitted to the mobilerouter 116. Thereafter, the mobile node 116 can register its currentlocation with the foreign agent 108. The foreign agent 108 in turnregisters with the home agent 104 (Step 616).

In accordance with an embodiment of the present invention, since theclients rely on the beacons and probe responses rather than the IRDPmessages, the rate at which foreign agent 108 send IRDP messages doesnot have to be every, for example, 3 seconds but can be relaxed toevery, for example, 30 seconds. Sending fewer IRDP messages from theforeign agent 108 eases up congestion of the wireless communicationnetworks 110, 112, 113 with IRDP messages.

There are certain situations or embodiments where a mobile node ismoving along the regional boundary between two access points. In thosesituations, for example, the system and method in accordance with anembodiment of the present invention does not need to constantlyre-register the mobile node in one region or another. Specifically,hysteresis can be built into the authentication and association phasesof a layer 2 handoff. By preferring handing off to access points in thesame region, a certain amount of hysteresis can be built into theprocess.

The features of the embodiments of the present invention may beimplemented in hardware, software, firmware, or a combination thereofand utilized in systems, subsystems, components or subcomponentsthereof. When implemented in software, the elements of the invention areprograms or the code segments used to perform the necessary tasks. Theprogram or code segments can be stored in a machine readable medium ortransmitted by a data signal embodied in a carrier wave over atransmission medium or a communication link. The “machine readablemedium” may include any medium that can store or transfer information.Examples of a machine readable medium include electronic circuit,semiconductor memory device, ROM, flash memory, erasable ROM (EROM),floppy diskette, CD-ROM, optical disk, hard disk, fiber optic medium,radio frequency (RF) link, etc. The code segments may be downloaded viacomputer networks such as Internet, Intranet, etc.

Although the invention has been described above with reference tospecific embodiments, the invention is not limited to the aboveembodiments and the specific configurations shown in the drawings. Forexample, some components shown may be combined with each other as oneembodiment, or a component may be divided into several subcomponents, orany other known or available component may be added. The operationprocesses are also not limited to those shown in the examples. Thoseskilled in the art will appreciate that the invention may be implementedin other ways without departing from the sprit and substantive featuresof the invention. The present embodiments are therefore to be consideredin all respects as illustrative and not restrictive. The scope of theinvention is indicated by appended claims rather than by foregoingdescription, and all changes that come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed is:
 1. A method performed for facilitating rapidhandoffs in a mobile network between access points, comprising:receiving, by a first access point, at least one service availabilityadvertisement, wherein the at least one service availabilityadvertisement includes an Internet Control Message Protocol RouterDiscovery Protocol (IRDP) message; extracting, by the first accesspoint, service availability content from the at least one serviceavailability advertisement; appending, by the first access point, theservice availability content into at least one rapidly repeatedmanagement packet transmission, wherein the appending of the serviceavailability content into at least one rapidly repeated managementpacket transmission includes generating a new field in a managementframe of the management packet, the new field being populated with theIRDP message; transmitting, by the first access point, the appendedrapidly repeated management packet transmission, the appended rapidlyrepeated management packet including the IRDP message being transmittedmore frequently than the at least one service availability advertisementis received; and receiving, by a second access point, the appendedrapidly repeated management packet transmission, such that a Layer 3handoff occurs, wherein the mobile network is a Mobile Internet Protocol(IP) network, and the at least one rapidly repeated management packet isone of a beacon message and a probe response.
 2. The method of claim 1,wherein the service availability content includes at least one of: anaddress of a foreign agent, a Registration Lifetime, a number of Care ofAddresses, at least one Care of Address, a home agent flag, and aforeign agent flag.
 3. The method of claim 2, wherein the serviceavailability content further includes a region indicator integer.
 4. Themethod of claim 3, wherein the region indicator integer is stored in anobject identifier preprogrammed in an associated access point via the atleast one service availability advertisement, the region indicatorinteger representing a specific region of coverage by the associatedaccess point.
 5. The method of claim 1, wherein the at least one serviceavailability advertisement is received from a layer 2 region.
 6. Themethod of claim 1, wherein the at least one service availabilityadvertisement indicates soon-entry from a first layer 2 region to asecond layer 2 region, the first and second layer 2 regions beingdifferent.
 7. The method of claim 1, wherein the first access pointtransmits IRDP messages at a further reduced rate.
 8. The method ofclaim 1, further comprising: after the first access point extractsservice availability content from the at least one service availabilityadvertisement, storing the service availability content in a table, thetable being at least one of local to the first access point, remote tothe first access point, and composed of a plurality of tables.
 9. Amethod performed via a Mobile Internet Protocol (IP) network node forfacilitating rapid handoffs in a Mobile IP network, comprising:receiving, at the Mobile IP network node, a management packet havingservice availability content from an access point, wherein the serviceavailability content includes an Internet Control Message ProtocolRouter Discovery Protocol (IRDP) message; extracting, with the Mobile IPnetwork node, the service availability content from the managementpacket; composing, with the Mobile IP network node, a networkregistration message based upon the extracted service availabilitycontent; and transmitting, with the Mobile IP network node, the networkregistration message, wherein the management packet is one of a beaconmessage and a probe response such that the included IRDP messagefacilitates a rapid handoff occurring via Layer 3 of the Mobile IPnetwork between two access points.
 10. The method of claim 9, whereinthe service availability content includes at least one of: an address ofa foreign agent, a Registration Lifetime, a number of Care of Addresses,a Care of Address, a home agent flag, and a foreign agent flag.
 11. Themethod of claim 10, wherein the service availability content furtherincludes a region indicator integer.
 12. The method of claim 11, whereinthe region indicator integer is stored in an object identifierpreprogrammed in an associated access point via the at least one serviceavailability advertisement, the region indicator integer representing aspecific region of coverage by the associated access point.
 13. Themethod of claim 9, wherein the service availability content waspreviously extracted from at least one service availabilityadvertisement including the IRDP message before being appended into themanagement packet.
 14. The method of claim 13, wherein the at least oneservice availability advertisement indicates soon-entry from a firstlayer 2 region to a second layer 2 region, the second layer 2 beingassociated with the access point, the first and second layer 2 regionsbeing different.
 15. The method of claim 9, further comprising: afterthe Mobile IP network node receives the management packet, validatingthe management packet by the Mobile IP network node.
 16. The method ofclaim 15, wherein the validating includes: identifying an SSID and aCare of Address in a management frame of the management packet,confirming that the SSID is valid, confirming that the Care of Addressis an available Care of Address, wherein if both the SSID and Care ofAddress are successfully confirmed, then the composing of the networkregistration message includes generating the SSID and the Care ofAddress into a new service availability advertisement which istransmitted as the network registration message.
 17. The method of claim16, wherein if at least one of the SSID is confirmed as invalid and theCare of Address is confirmed as unavailable, then the Mobile IP networknode discards the management packet.
 18. The method of claim 17, whereinthe transmission of the network registration message involves aregistration of location by the Mobile IP network node with a home agentof the Mobile IP network node via the access point.
 19. An apparatus forfacilitating rapid handoffs in a mobile network, comprising: an accesspoint, wherein the access point is configured to: receive, with areceiver, at least one service availability advertisement, wherein theat least one service availability advertisement includes an InternetControl Message Protocol Router Discovery Protocol (IRDP) message;extract, with a processor, service availability content from the atleast one service availability advertisement; append, with theprocessor, the service availability content into at least one rapidlyrepeated management packet transmission, wherein the appending of theservice availability content into at least one rapidly repeatedmanagement packet transmission includes generating a new field in amanagement frame of the management packet, the new field being populatedwith the IRDP message; and transmit, with a transmitter, the appendedrapidly repeated management packet transmission to another access pointsuch that a Layer 3 handoff occurs, the appended rapidly repeatedmanagement packet including the IRDP message being transmitted morefrequently than the at least one service availability advertisement isreceived; wherein the mobile network is a Mobile Internet Protocol (IP)network, and the at least one rapidly repeated management packet is oneof a beacon message and a probe response.
 20. The apparatus of claim 19,wherein the one of the beacon message and probe response has a frameheader and a frame body, the frame header including a source anddestination Medium Access Control (MAC) addresses, and the frame bodyincluding at least one of a Service Set Identifier (SSID), a timestamp,a transmission interval, a parameter set, the parameter set includingIRDP message information which had been extrapolated from the IRDPadvertisement, a Registration Lifetime, a home agent flag, and a foreignagent flag.
 21. An apparatus for facilitating rapid handoffs in a MobileIP network, comprising: a Mobile IP network node, wherein the Mobile IPnetwork node is configured to: receive, with a receiver, a managementpacket having service availability content from an access point, whereinthe service availability content includes an Internet Control MessageProtocol Router Discovery Protocol (IRDP) message; extract, with aprocessor, the service availability content from the management packet;compose, with the processor, a network registration message based uponthe extracted service availability content; and transmit, with atransmitter, the network registration message, wherein the managementpacket is one of a beacon message and a probe response such that theincluded IRDP message facilitates a rapid handoff occurring via Layer 3of the Mobile IP network between two access points.
 22. The apparatus ofclaim 21, wherein the one of the beacon message and probe response has aframe header and a frame body, the frame header including a source anddestination Medium Access Control (MAC) addresses, and the frame bodyincluding at least one of a Service Set Identifier (SSID), a timestamp,a transmission interval, a parameter set, the parameter set includingIRDP message information which had been extrapolated from the IRDPadvertisement, a Registration Lifetime, a home agent flag, and a foreignagent flag.